1. Field of the Invention
The present invention relates to gas turbine engines, and more particularly to a fuel nozzle for such gas turbine engines.
2. Background Art
Fuel nozzles of gas turbine engines usually comprise a fuel distributor for dividing the fuel in several equal streams in order to develop a uniform fuel film. The fuel distributor is often also responsible for swirling the fuel streams to obtain a good fuel spray distribution.
Fuel distributors usually comprise a sealed disk element having a plurality of circumferentially spaced apart small metering holes or slots. The disk is usually mounted on a cylindrical channel adapted to deliver the fuel. The small metering holes are drilled with an axial as well as a circumferential orientation in order to provide a swirl to the fuel passing therethrough.
This configuration poses several problems, one of which is the fact that drilling identical holes of such a small size can be very difficult. If sufficient similarity between metering hole sizes is not achieved, the fuel film is not uniform, causing a poor spray quality. In addition, holes of such a small size are very susceptible to contamination or plugging.
Another problem with the prior art is that the channels upstream of the metering holes are exposed to a high amount of heat input through adjacent walls due to external heat transfer from hot air to the cool walls. This can lead to coke formation and hole plugging.
Also, the resistance of the metering holes is often insufficient to reach the desired nozzle resistance value, and a tuning orifice is often required at the inlet of the nozzle to compensate.
Finally, the disk is usually sealed with braze to prevent unmetered fuel from escaping around the metering holes. This presents a risk in manufacturing since braze can run into the metering holes, blocking them after the braze sets.
Accordingly, there is a need for an improved fuel distributor that overcomes the above-mentioned problems of the prior art.